Preparation And Characterization Of Selfhealing Rubber Based On Zinc Dimethacrylate Ionic Bonds

Rubber materials are always susceptible to mechanical damage during processing and use.It finally leads to catastrophic failure of the rubber,resulting in material waste and environment damage.In order to improve the durability of rubber,different type of reversible cross-links has been introduced into the cross-linked network structure of rubber in this thesis.Those reversable connections can automatically repair the damage,effectively prolonging the service life of rubber.In this thesis,natural rubber(NR)and butyl rubber(IIR)are used as the main rubber components,and zinc dimethacrylate(ZDMA)is used as the provider of ionic bonds,or ionic clusters.By controlling the vulcanization process,ZDMA is grafted to the rubber molecular chain.A reversible supramolecular network composing of covalent cross-linking,ionic cross-linking,and physical entanglement is formed.Experiments show that the repair efficiency of the NR/ZDMA compound is 59 % within the healing time of only 30 min at room temperature.When the healing time is extended to 5 h,the repair efficiency is as high as 99 %.The addition of IIR improves the physical properties of the whole system.The entanglements provided by IIR benefits the physical repair behavior.Meanwhile,it is also helpful for the dispersion of ZDMA in the system.The better blending effect of NR-IIR can help fix the free molecular chains in the system and increase the storage modulus of the rubber compound.Secondly,in this project,cis-butadiene rubber(BR)and butyl rubber(IIR)have been used as the main rubber components to prepare rubber compound.The compounding depends on a two-step method.First,in the presence of DCP,ZDMA is polymerized to form p-ZDMA.Then during the vulcanization process,p-ZDMA was grafted into the rubber network,forming a reversible supramolecular network composed of covalent,and ionic crosslinks.Experiments show that the repair efficiency of BR/ZDMA compound is 40 % within 30 min healing time.The repair efficiency increases to 77 % when the healing time is extended to 5 h.When the dosage of ZDMA is 40 phr,the BR and BR-IIR compound had the best mechanical properties,which were 1.71 MPa and 2.85 MPa,respectively.The addition of IIR increased the activation energy of the reaction system and increased the degree of cross-linking of the rubber samples.In this thesis,the self-healing behavior of ring-opened epoxidized natural rubber(ENR)has also been studied.ENR was first treated under acidic conditions to generate a ring-opening product with hydroxyl(-OH)group.Then,it reacted with diphenylmethane diisocyanate(MDI)and the graft with p-ZDMA.The reversible hydrogen-bonding structure and partial ionic cross-linking are introduced into the cross-linked network of ENR.By controlling the vulcanization process,multiple reversible supramolecular networks composed of reversible hydrogen bonds,ionic crosslinks and covalent crosslinks were formed.ENR self-healing elastomer materials with excellent self-healing ability and mechanical properties were successfully prepared.Experiments show that the selfhealing efficiency of ENR self-healing material is as high as 69 % within the healing time of 30 min,which is significantly greater than the selfhealing efficiency of NR/ZDMA compound under the same repair conditions.The hydrogen bond structure plays the role of cross-linking and entanglement,firmly fixing the molecular chain,restricting the movement of the molecular chain.It made the chains are not easy to break when stretched,and showing the best tensile strength under small strain.